In the field of photography, water-insoluble matting agents have been used in top layers or back layers of photographic materials to prevent adhesion when materials are stored in the rolled state in conditions of relatively high humidity and temperature, to prevent electrostatic charges by reducing the area of contact of the photographic material, to prevent the formation of Newton's rings during printing and enlargement, or to decrease the occurrence of scratches during storage or packing of the photographic material.
It is known that matting agents insoluble in alkaline processing solutions, such as silica and polymethylmethacrylate, remain in the processed photographic material. The photographic material therefore has a slightly milky appearance which detracts from the image formed therein.
To avoid such problems, matting agents which are insoluble in neutral or acid solutions and are soluble in alkaline medium have been described in the art. Such matting agents are incorporated in the photographic layers in the form of discrete particles by dispersing a solution of the matting agent in a water-immiscible organic solvent in an aqueous gelatin solution, eliminating the organic solvent, and then introducing the obtained dispersion into the coating composition of the photographic layer. Organic solvents or combinations thereof have been studied with the copolymers of methylmethacrylate and methacrylic acid, the basic solvent being butanol and mixtures thereof with other solvents. Since however butanol is a low volatile solvent, it must be removed by cooling the dispersion and washing it with deionized water. A part of the solvent remained even after prolonged washing of the dispersion which also retained an objectionable odor. Furthermore, industrial water could not be used in the washing because cations present therein caused substantial dissolution of the polymeric particles.